While production techniques and markets for frozen food products are well developed, important advances continue to be made. In particular, continuing developments are directed to further preserving the flavor, and maintaining the moisture, appearance and integrity of frozen food products.
For example, cryogenic freezing, which involves a very fast, low-temperature freeze of a food product, is being perfected to yield products which are less dehydrated and more tender, and which exhibit less shrinkage. Further, such freezing yields effective pasteurization, i.e., rendering bacteria dead or inactive, as evidenced by a greatly reduced plate count, e.g. 80% to 98% reduction, thereby resulting in longer shelf lives and overall increased product integrity.
With the continuing development of such techniques, consumer demand for products continues to increase. Consequently, freezer system throughput and attendant space requirements have become particularly acute design considerations for established production facilities. That is, since the facilities necessary to produce frozen food products are typically capital intensive, the general objective among food producers is to accommodate the implementation of new developments within the limitations of their existing facilities. This objective, in turn, puts a premium upon approaches for implementing new technologies which will also increase throughput and maintain or reduce space requirements.
Most recently, in an attempt to address at least some of the above-noted considerations, a tunnel-spiral freezer system was developed. The food product is initially crust frozen in a liquid nitrogen tunnel and then frozen completely in a spiral freezer. Crust freezing the food product inhibits dehydration of the food product, thereby allowing the food products to be placed in contact with one another as the food products are completely frozen. However, the tunnel-spiral freezer presents certain drawbacks.
Specifically, if liquid nitrogen is used in the tunnel portion, gaseous bubbles of vapor can form on the lower side of the food product as it travels through the liquid nitrogen bath due to the heat transfer from the food product to the liquid nitrogen. These bubbles inhibit the crust freezing and the resultant partially frozen food products stick together, or "twin," resulting an unaesthetic appearance . Additionally, the nitrogen tunnel can present safety concerns due to the nitrogen vapor exhaust.
Finally, where a liquid nitrogen tunnel is utilized, significant refrigeration inefficiencies can be experienced due to tunnel energy losses.